A1 is definitely displaced, but the ball is so far away that he isn't really at a disadvantage to recover it.
After thinking about it:
After A1 lands, he's just a player without the ball who runs under the location that B1 will land. You could almost call a foul on A1 for not acquiring verticality before B1 left the ground (just kidding).
This situation is much different than if A1 were shooting a simple jumpshot. In that case, you call the foul on B1 for jumping into the space on the floor occupied by A1.
For the original situation, no call - incidental contact.
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Luther
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